<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>利用原型对象扩展内置对象方法</title>
</head>
<body>
  <script>
    // 原型对象的应用 扩展内置对象方法

    Array.prototype.sum = function () {
      var sum = 0
      for (var i = 0; i < this.length; i++) {
        sum += this[i]
      }
      return sum
    }
    // Array.prototype = {
    //   sum: function () {
    //     var sum = 0
    //     for (var i = 0; i < this.length; i++) {
    //       sum += this[i]
    //     }
    //     return sum
    //   },
    // }
    var arr = [1, 2, 3]
    console.log(arr.sum())
    console.log(Array.prototype)
    var arr1 = new Array(11, 22, 33)
    console.log(arr1.sum())
  </script>
</body>
</html>